In the making of hollow blown plastic articles such as containers, it has heretofore been suggested that labels be held in one or more of the mold sections by vacuum so that when the parison is blown outwardly into conformity with the cavity, the label becomes adhered or bonded to the article.
The molds are often provided in a plurality of sets of partible molds in a predetermined array and, in order to delivery the labels, a plurality of magazines are provided, one for each mold half, and an associated plurality of pick-up and delivery devices function to remove labels from the magazines and deliver them to one or both of the mold halves of each set.
As set forth in U.S. Pat. No. 4,636,166, having a common assignee with the present application, an apparatus is provided wherein labels are successively removed from a label magazine and positioned in an array which corresponds in spacing to the spacing of the sets of molds. The labels are then simultaneously moved in the array from the first position to a second position within the open partible molds and deposited in the molds. The apparatus comprises a magazine for supporting labels in a stack and an endless belt transfer device positioned adjacent the magazine. The belt is indexed in predetermined spaces corresponding to the spaces of the array of molds. A label pick-up device removes a label from the magazine and deposits it on the conveyor so that the spacing between the labels on the endless transfer conveyor corresponds to the spacing between the sets of molds. Another label deposit device removes the labels simultaneously from the endless transfer conveyor and delivers them between the open partible molds.
In my copending application Ser. No. 054,928, filed May 28, 1987, having a common assignee with the present application, a method and apparatus is disclosed which comprises providing labels on a roll of labels, successively engaging the free end of the web of the roll of labels by a first endless vacuum conveyor, tensioning the portion of the web between a point upstream and the free end by the first endless vacuum conveyor, successively cutting a label on the free end from the remaining tensioned portion, transferring each label successively by moving the first endless conveyor adjacent a second endless vacuum conveyor which is transverse to the first conveyor, indexing the second endless conveyor to provide an array of labels on the second endless conveyor which corresponds in spacing to the spacing of the array of molds, engaging the array of labels and moving them from a first position adjacent said second conveyor to a second position within the partible molds and depositing the labels in the molds.
Where an endless conveyor belt is utilized to receive the labels and position them in the predetermined array for delivery to the open partible molds, a problem occurs because of the slippage between the endless conveyor and the roller. More specifically, when the drive roller is rotated, the belt is driven through friction between the roller and the belt. The distance or amount that the belt is moved depends on the amount of slippage between the belt and roller as well as the pitch diameter of the belt and roller as the belt feeds over the roller. Even if the slippage is eliminated, changes in the extent of movement of the belt occur as the pitch diameter changes. These changes in pitch diameter occur because changes in belt flexibility occur especially where the endless belt is spliced from a length of belt.
Among the objectives of the present invention are to provide an apparatus for applying labels to blow molded articles which utilizes an endless conveyor wherein the movement of the belt is independent of changes in pitch diameter; wherein slippage is controlled; and wherein the conveyor is moved in precise predetermined increments obviating any cumulative air of movement in providing an array of labels.
In accordance with the invention, the apparatus for indexing an endless conveyor in precise increments for receiving longitudinally spaced labels providing an array of labels which are thereafter simultaneously removed from the endless conveyor and delivered between the open partible molds comprises a fixed conveyor gripper in a first position, a second conveyor gripper mounted for movement longitudinally of the belt and means for individually controlling the gripping of the first and second grippers such that the first gripper can be actuated to engage the conveyor and moved longitudinally to thereby move the conveyor a predetermined distance, the first gripper can then be engaged with the conveyor and the second gripper released and returned to its original position for moving the conveyor in successive and predetermined increments for precise positioning of the labels on the conveyor.